1. Field of the Invention
This invention relates to vinylpyrrolidones, and, more particularly, to 1-vinyl-3(E)-ethylidene pyrrolidone (EVP), and to a method for obtaining this isomeric compound.
2. Description of the Prior Art
Crosslinked polyvinylpyrrolidone (PVP) is made by popcorn or proliferous polymerization of vinylpyrrolidone (VP), in the absence or presence of crosslinking agents, as described in U.S. Pat. Nos. 3,277,066; 3,306,886; 3,759,880; 3,933,766; and 3,992,562; and in an article by F. Haaf et al. in Polymer J. 17 (1), p. 143-152 (1985), entitled, "Polymers of N-Vinylpyrrolidone: Synthesis, Characterization and Uses". Polymerization of vinylpyrrolidone can occur in the absence of added crosslinker because the requisite crosslinker in the process is formed in situ during the first stage heating of vinylpyrrolidone in aqueous caustic solutions at temperatures&gt;100.degree. C., e.g. at 140.degree. C. Such bifunctional monomers, identified as 1-vinyl-3-ethylidene pyrrolidone and ethylidene-bis-3-(N-vinylpyrrolidone), are observed by gas chromatography and other analytical techniques to be present in small amounts in reaction mixtures which had been cooled to room temperature. However, after the polymerization was completed, these bifunctional compounds, could not be found in the final product. Accordingly, the named bifunctional monomers are present only in small amounts as intermediates during the polymerization and are consumed in the process of forming the crosslinked PVP polymer.
Accordingly, an object of this invention is to provide a process for obtaining the isomeric compound 1-vinyl-3(E)-ethylidene-pyrrolidone in a purity of at least 95%.
These and other objects and features of the invention will be made apparent from the following description of the invention.